A clinical positron emission tomography (abbreviated as PET below) device includes 30,000 detectors, and thus 30,000 electronic processing channels are needed for directly reading out electrical signals generated by the respective detectors. The large number of the electronic channels results in high cost and huge difficulty in engineering implementation of a whole PET electronics system.
In view of the above, researchers focus on studying and developing channel multiplexing technology for reading out detector signals. An existing mainstream readout channel multiplexing method is to weigh outputted detector signals based on rows and columns through a resistance network and then read out the output signal.
By multiplexing with the resistance network, the number of readout channels for the detectors is reduced, which solves the problem of excessive channels. However, with the resistance network, equivalent resistances of the resistance network for different detectors are different due to different signal access points, which results in a large difference among amplitudes of output signals of the different detectors. In this case, a large dynamic range is required for a back-end readout circuit. Existing processing circuits normally have a limited dynamic range, that is, a small inputted signal will result in a low signal-to-noise ratio, while a large inputted signal will result in a saturation problem.
Accordingly, in view of the above technical problems, it is necessary to provide a channel multiplexing method providing an improved structure for reading out detector signals, to overcome the above shortcomings and effectively solve the problem of an excessive dynamic range of the signals outputted by the detectors with channel multiplexing.